Re: [PATCH 09/11] sysfs: Push file_update_time() into bin_page_mkwrite()

Jan Kara [off-list ref] writes:

On Thu 16-02-12 13:04:44, Alex Elder wrote:

quoted

On Thu, 2012-02-16 at 14:46 +0100, Jan Kara wrote:

quoted

CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/sysfs/bin.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/fs/sysfs/bin.c b/fs/sysfs/bin.c
index a475983..6ceb16f 100644
--- a/fs/sysfs/bin.c
+++ b/fs/sysfs/bin.c

@@ -225,6 +225,8 @@ static int bin_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 	if (!sysfs_get_active(attr_sd))
 		return VM_FAULT_SIGBUS;
 
+	file_update_time(file);
+
 	ret = 0;
 	if (bb->vm_ops->page_mkwrite)
 		ret = bb->vm_ops->page_mkwrite(vma, vmf);

If the filesystem's page_mkwrite() function is responsible
for updating the time, can't the call to file_update_time()
here be conditional?

I.e:
	ret = 0;
	if (bb->vm_ops->page_mkwrite)
 		ret = bb->vm_ops->page_mkwrite(vma, vmf);
	else
		file_update_time(file);

  Hmm, I didn't look previously where do we get bb->vm_ops. It seems they
are inherited from vma->vm_ops so what you suggest should be safe without
any further changes. So I can do that if someone who understands the sysfs
code likes it more.

I do.  Essentially sysfs is being a stackable filesystem here, because
sysfs needs the ability to remove a file mapping.

In practice we could probably get away without a single
file_update_time(file) here because there are mmio mappings.  Normally
for pci resources, but we might as well use good form since we can.

Eric

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